I have some 'full cover' knickers that definitely show above the waistband of my work trousers. I figure it's something to do with a. my work trousers (as with the majority of my trousers atm - I seem to have settled clothing size in between two sizes) being both mid-rise and 1/2 size too big, and b.'full cover' knickers sitting at or above my navel!
Of course, I either wear my tees tucked in or a longline cami under untucked/short tees as applicable anyway since I dislike drafts up my back, so my knickers aren't generally visible!